IF YOU want to know a salmon’s social status just gaze into the whites of its
eyes.
Hayley Suter and her colleagues from the University of Glasgow’s fish biology
unit studied the sclera, or “whites”, of Atlantic salmon’s eyes, and found that
the colour was linked to the social status, belligerence and hunger of each
fish. Dominant fish had light, cream-coloured sclera that only darkened if they
fell ill. Low-status fish had dark sclera that lightened only after they ate a
meal or won a battle.
Just a tiny amount of food made a noticeable change, says Suter, who reports…
